Solvent extraction of aromatic from aliphatic hydrocarbons using beta hydroxy ethyl-m-tolyl sulfide or beta hydroxy ethyl phenyl sulfide



United States PatentO SOLVENT EXTRACTION OF AROMATIC FROM ALIPHATIC HYDROCARBONS USING BETA HYDROXY ETHYL-M-TOLYL SULFIDE OR BETA HYDROXY ETHYL PHENYL SULFIDE Charles 0. Petty, Tyler, Tex., assignor of one-half to The La Gloria Oil and Gas Company, Tyler, Tex., a corporation of Delaware No Drawing. Original application Oct. 29, 1957, Ser. No. 693,040. Divided and this application Apr. 28, 1959, Ser. No. 809,338

3 Claims. (Cl. 208-322) This invention is a division of my copending application Serial No. 693,040, filed October 29, 1957, now US. Pat. No. 2,927,946, which in turn is a continuationin-part of my copending application Serial No. 565,289, filed December 21, 1955, now US. Pat. No. 2,862,804 and relates to a phenol catalyzed reaction of organic thiol compounds with epoxides, to purification of crude commercial acid phenolic oils to remove sulfur compounds, and to novel composition of matter comprising the reaction product of organic thiol compounds with epoxides formed in that reaction.

According to this invention I have discovered that a pure phenol or commercial mixtures of acid phenolic lcompounds, or solutions of acid phenols containing phenols in substantial concentration, usually exceeding about 5 volume percent of a commercial phenol solution in a solvent, catalyzes the reaction between an organic epoxide and an organo thiol (mercaptan). Such mercaptans usually occur as impurity in the commercial phenols, whereby the mercaptans are converted to hydroxy hydrocarbon thiol ethers and the commercial phenol can be purified thereby either merely to deodorize or by further treatment to remove the sulfur compounds.

Notwithstanding epoxides are known to react readily with phenols, I have found that the epoxide will react selectively and preferentially with the organic thiols in the presence of, a large quantity of phenols at ambient to moderately raised temperatures up to about 75 (3., even when the thiols are present in admixture with the phenols in very small or trace quantities. The selective thiol reaction takes place at low, such as ambient temperature, and to a substantial degree up to about onehalf to two hours more or less rapid depending on the character of the mercaptan. However, the yield becomes quantitative and the reaction runs more rapidly in the higher portion of the temperature range.

The reaction product of the expoxide with the thiols, particularly thiophenols and thiocresols comprising hydroxy hydrocarbon thioethers are valuable products per se which are useful in certain applications such as an extraction solvent to selectively separate aromatic type hydrocarbon from aliphatic type hydrocarbon and as stabilizers for cracked gasoline.

Thus, according to the present invention crude commercial mixtures of phenols, such for example as crude tar acids separated as a tar acid oil fraction in coal tar distillation, or crude petroleum phenols separated from thermally or catalytically cracked petroleum naphthas which contain mercapto compounds such as thiophenols, thiocresols, thioxylenols, and lower molecular weight aliphatic mercaptans may be purified to convert the mercaptan, or even hydrogen sulfide contained as an impurity in the acid phenolic oil to thio ethers by reaction with the organo epoxide. Other commercial phenols, such as may be formed synthetically, for instance, where 1 Thiophenol (2) m-Thiocresol (3) N-amyl mercaptan As will be noted, that reaction is very actively and selectively catalyzed by the phenol present in substantially large quantities in the reaction mixture. It is surprisingly reactive because the phenol will catalyze that reaction to substantially quantitative yields whereby all of the mercapto compound is converted to epoxide derivative, for instance, hydroxy alkylene thio ether when the epoxide used is an alkylene oxide, and at a temperature up to about C.

The reaction is surprising in that phenols themselves, known to react with alkylene oxides, do not appear to react in the presence of the sulfur compounds at such moderately low temperatures so that the reaction goes to completion whereby the alkylene oxide may be substantially stoichoimetric with respect to the mercapto compound or may be used in slight excess as desired without substantial loss of phenols. The phenols, only in the presence of an excess of alkylene oxide and at a temperature above about 75 C., begin to react with the excess alkylene oxide after the mercaptans have reacted. As stated, the reaction goes to completion and it may be slightly accelerated to reduce the reaction time by raising the temperature from about ambient, such as 25 C., up to about 75 C. Although substantially raised temperatures are not esential it is preferred to carry out the reaction in the temperature range of about 40 to 60 C. to enhance the reaction rate.

The term epoxide as used herein is intended to define a compound containing an olefine oxide group having the following structure:

wherein R is a 1 or 2 carbon atom alkyl, or hydrogen, because these are more easily handled, and react more eases! rapidly and efliciently. Useful higher epoxides usually for purposes other than sweetening include amylene oxide, cyclohexene oxide, styrene oxide, epichlorohydrin, glycide, .decene oxide, butadiene oxide and the like.

While, as indicated, other epoxides are useful and any of the type mentioned above will be used to 'form corresponding hydroxy hydrocarbon thio ether derivatives of the mercaptans present in the phenolic oil, where the commercial phenolicoil is merely to be purified as a primary objective to obtain pure phenols free of mercaptan, it is preferred to use a lower alkylene oxide, usually having up to 5 carbon atoms, preferably 2 or 3, typical. examples of which are ethylene oxide, propylene oxide, butylene oxide and amylene oxide.

The crude phenolic acid oil usefully purified by the present invention comprises a5 to 100 volume precent phenolic oil solution. Such solution may contain from mere traces, i.e. less than .00001 percent of organic mercaptan, up to a highly contaminating quantity of'rnercaptan such as to or higher. The remainder of the solution comprises phenols, other acidic substances often occurring therewith in commercial phenolic extracts such as naphthenic acids, and solvents such as water, hydrocarbon and the like.

In the practice of this invention the epoxide may merely be added in slight molar excess to the mercaptan content of the phenol solution, desirably with slight warming of the solution. It is sometimes desirable, but not neces sary, to add the ethylene oxide dissolved in a hYdIOQarbon solvent. preferably an aliphatic type naphtha, for example, gasoline comprising a C to C hydrocarbon fraction of a virgin 'naphtha comprising hexane or heptane, etc., in concentration from 2 to 5% epoxide in the hydrocarbon by volume. That hydrocarbon solution is then agitated with the sulfur Cont minated phenolic. acid oil in quantity. such that the epoxide is at least sufiicient to react with the mercaptan sulfur present. That reaction, as stated, may take place at ambien'tte'mperature'up to 75 C., but preferably the temperature is held to" the range from about 40 to 60 C. By proper selection of a solvent the combined mixing, heating and timing of the reaction may be effected by' selection of a hydrocarbon solvent boiling in this range, such as a narrower cut petroleum naphtha, and heating the mixture to reflux. Higher pressures may be used where the'method is applied as part of a synthetic production or refining system operating under pressure; orto prevent vapo'rization'during the contact, butotherwiSe raised pressures are not essential for this reaction.

The hydroxy hydrocarbon thio ethers formed are preferentially soluble in the 'hydrocarbonsolvent. Any phenols tending as such to dissolve in the hydrocarbon solvent may be washed or extracted out with water. Alternatively after finally extracting the sulfur compounds from the acid phenolic oils, any phenolic oils remaining in the hydrocarbon solvent solution of thio ethers may be extracted with aqueous alkali. That aqueous alkali solution may be acidified and returned to the sulfur free phenolic oil raffinate. i

The purified acid phenolic oils may be distilled to separate individual phenols as desired.

The hydroxy thio ether reaction product dissolved in hydrocarbon solvent is then purified by distilling off the solvent and fractionally distilling to separate pure hydroxy alkylene thio phenols and cresols or other thio e s pr s n d ndin up the p t cu a or a epoxidethat was used.

While there are advantages to obtaining high yields and ready extraction of the thio ethers formed in the phenolic oil when the epoxide is dissolved in a hydrocarbon solvent before contact with mercaptan containing phenolic oil, the epoxide can merely be added directly to the mercaptan containing phenolic oil without a solvent and the solution agitated and/or warmed to reaction underitefiux of the epoxide. The mercapto compounds when pres n in mere traces need not be removed, the phenolic oil being merely sweetened by this reaction to convert the malodorous mercaptans to thio ethers. Moreover, larger quantities of thio ethers may be removed by distillation since they usually boil at temperatures substantially higher than the phenols and will be 're'covered as residue when t e ph s. a e st ll Moreover, it is found that the epoxides, particularly the lower alkylene epoxides, react with aromatic mercaptans present in the, acid phenolic'oil such as thio phenols, more rapidly at lower temperatures than with the ali pha tic mercaptans; Accordingly, it is po'ssible'to obtain additional selectivity by first reacting'the mercaptan con taminated phenolic oil with the epoxides, such as a lower alkylene oxide, at the low generally ambient temperatures such as below about 40. C. and for short periods of time such as less than about 30 minutes. These more aromatic thio ethers thus formed which will be predominantly hydroxy alkylene thiophenol ethers, may be extracted with a solvent from the other less reactive mercaptans contained in the phenolic oil. Alternatively thio ethers may be separated from the phenols and aliphatic meraptan's by distillation since contaminating and apparently slower reacting aliphatic mercaptan will remain in the phenolic oil raffinate or distillate.

Of course, as indicated above, all of the mercaptan compounds may be caused to react by heating up to about C., preferably in the range of 40 to 60 C., for short periods up to'about 'onehour, usually less than 30 minutes, such as about '15 minutes, or for longer periods from about 1 to 2 hours depending "upon the epoxide andcharacter of the mercaptans.

Moreover, epoxides such as the lower alkylene oxides will react quantitatively with all of the mercaptan that may be present in the phenolic" oil at ambient tempera- .ture if-asufficientquantity of epoxide is used, at least 'stoichiornetri'c to the mercaptan present; providing sufs ficient time of c'ont'act'is allowed between the reagents. Thus, the aromatic mercaptans such as thiophenols and thiocresols react rapidly and at lower temperatures with the epoxide. The aliphatic mercaptans react very slowly at low temperatures. Hence, the mixture of mercaptancontaining phenols containing some aliphatic mercaptan needs to be contactedfor about 3 10 hours and sometimes longer at-ambient temperature for complete reaction." However, as "statedywarmin'g slightly will cause the reaction to go to completion in a'muchshorter period.

The reaction of the thiophenol withthe lower alkylene oxide such as ethylene oxide, appears to be exothermic and rapid, whereas reaction of the ethylene oxide with other mercaptans may be more slow and endothermic.

grams of a commercialmixture of tar acids formed by distilling coal tar and obtained as a carbolic oil comprising a fraction of the tar distilling in the .rangeof to 2309 C. and containing 1.2 grams of mercapto compounds predominantly thiophenols, was treated by passing 3 grams of ethylene oxide gas into the acid phenolic oil over-a period of 30 minutes whilemaintaining the acid oil .ata' temperature of 55-? C. and'withgrapid agitation, the excess'ethylene oxide being returned-to the reaction mixture as reflux from an ice cooled condenser. The said phenolic oil was ,found to have a coppernurnher of zero which indicated that no free mercaptan remained Acid oil extract of catalytic naphtha Temp, Specific Per- Per- Fraction F. Gravity cent cent of N o.

RSH Total Cat. Naphtha Acid Oi1 1. 0215 8. (311-438) Distillation:

IBP-- 311 A fraction comprising a first fraction boiling up to 378 F. and comprising 14.3% of the total acid phenol distillate containing 9.5% of mercaptan had a total of two grams of gaseous ethylene oxide (about 200% theoretical) bubbled through the liquid with agitation over a period of 5 minutes, no extraneous heat being applied, some slight warming up to about 40 F. taking place by the heat evolved by reaction, the excess unreacted ethylene oxide being continuously returned to the reaction mixture by an ice cooled reflux condenser. After 5 minutes the excess ethylene oxide was removed by allowing it to evaporate at room temperature and the mercaptan content of the oil was analyzed and found to be reduced approximately 20%. The second fraction of the distillate oil having the characteristics set forth on the table was treated similarly and with the same quantity of ethylene oxide. The mercaptan content of that fraction was found to be reduced 85%. In a similar way the third fraction of the table similarly treated was found to have its mercaptan content reduced 95% and the fourth fraction 100%. The experiment shows that the order of reactivity of the higher mercapto compounds appearing in the higher boiling fraction is much greater, and the aromatic thio phenols associated with the higher boiling fractions are reacted more rapidly and to a greater degree at low temperature.

EXAMPLE III The experiment of Example H was repeated with the first three fractions except that the phenolic oil in each case was heated to 60 C., the excess ethylene oxide being continuously returned to the Warm phenolic oil as reflux from the ice cooled condenser. In a period of 30 minutes of heating under these conditions, analysis of the first fraction showed no mercaptan sulfur remaining in the phenolic oil. Similarly fractions two and three showed no mercaptan remaining in the phenolic oil.

EXAMPLE IV In order to check the rate of reaction against a pure synthetic mixture, a 100 gram mixture of pure metacresol in quantity of 98%, thiophenol in quantity of 1%, and metathiocresol in quantity of 1%, all quantities being by weight, were shaken for minutes with 2 grams of ethylene oxide, at room temperature of 24 C. in a closed bottle and the mercaptan was analyzed and found to be reduced. The shaking was continued at room temperature and after minutes total time the mixture again was analyzed and the mercaptan found to be 60% reduced. The shaking was again continued and the mixture again analyzed after an hour and the mercaptan was found to be reduced, and finally, after shaking for a total'time of 1% hours the mercaptan was found to be converted to the thio ether.

EXAMPLE V Another synthetic 100 gram mixture was made using 97.5% of pure metacresol, 1% thiophenol, 1% metathiocresol and 0.5% of N-butyl mercaptan, all quantities being by weight. This mixture, as in Example IV, was shaken at the same ambient temperature with 3 grams of ethylene oxide in a bottle. Analysis after 15 minutes EXAMPLE VI The composition of Example V was heated under reflux at 60 C. with 2 grams of ethylene oxide and analyzed after 15 minutes and there was found to be no mercaptan sulfur present. The heating was continued for a period of 2 hours at 60 C. and ethylene oxide was distilled ofi recovering most of the theoretical excess, about 1 gram. This experiment indicated that heating at a temperature of 60 C. quickly drives the reaction to completion but heating at that temperature for a long period of time does not cause the phenol present to react with the ethylene oxide whereby it is clear that the reaction is indeed selective.

EXAMPLE VII EXAMPLE VIII The thio ether containing reaction product of Example .VII was distilled first at atmospheric pressure at 405 F.

to remove unreacted phenols and the residue was further distilled in vacuum. A fraction boiling at 514 F. at 750 mm. Hg was recovered. This appeared to be the beta hydroxy ethyl ether of thiophenyl sulfide, as in Equation 1 above. It analyzed 61.1% carbon, 6.3% hydrogen and 19.2% sulfur and had a freezing point of 10 F. Another fraction recovered at a boiling point of 530-535 F. and 751 mm. Hg appeared to correspond to beta hydroxy ethyl m-tolyl sulfide as illustrated in Equation 2 above. It analyzed 63.8% carbon, 7.1% hydrogen and 18.7% sulfur. The beta hydroxy ethyl phenyl sulfide was mixed in equal volume with a synthetic mixture of 50% toluene and 50% N-heptane. The mixture was shaken and the extract analyzed by distilling the hydrocarbon from the extract. It was found to comprise 98% toluene and the ralfinate analyzed 98% N-heptane thereby indicating that the hydroxy alkyl thiophenyl ether is a highly selective solvent for separation of aromatic from aliphatic hydrocarbon contained as a mixture in a hydrocarbon naphtha.

EXAMPLE IX The beta hydroxy ethyl meta tolyl sulfide of Example VIII was added in. quantity of 0.1% by weight to a sweet ihe w rvaeke a snl ne a in @lind fljgnmtiodQ 'nd (copper 'di sh gum f'35 rug/100ml. ggid wgsfe nd hereafiter to have hnl'i n ductiqli'period of 4 /2 hours un er Refetencesfiitedin -.the fileof this patent -Eromm :.et 31.: Chem. Abstracts, vol. 15, page's 2%62, 12. .139!- X9 5. 13, pa es 3. 0-6, 2 

1. THE METHOD OF SEPARATING AROMATIC FROM ALIPHATIC HYDROCARBON CONTAINED IN A HYDROCARBON NAPHTHA MIXTURE COMPRISING EXTRACTING THE AROMATIC HYDROCARBON COMPONENTS WITH A COMPOUND SELECTED FROM THE GROUP CONSISTING OF BETA HYDROXY ETHYL PHENYL SULFIDE AND BETA HYDROXY ETHYL M-TOLYL SULFIDE. 